In household electrical appliances, audio visual appliances, personal computer equipment, office automation equipment, industrial machines or other electronic devices, a capacitive touch switch is used as one of input devices to each appliance.
FIG. 8 shows one example of the capacitive touch switch. FIG. 8 is a cross-sectional side view of the touch switch. In a capacitive touch switch 1′, a switch design 2a′ is formed on a glass cover 2′ by means of printing or laser trimming, and further a sensor electrode 3′ is arranged. Further, a control portion 10 and the touch switch 1′ are connected via flexible printed circuits (hereinafter, referred to as FPC) 4′. In the capacitive touch switch having such a configuration, when a surface of the cover 2′ is touched by a finger, electrostatic coupling is generated between the sensor electrode 3′ and the finger, and thereby capacitance of the electrode is changed. The sensor electrode 3′ is arranged at a plurality of positions corresponding to the switch design. A wire is assigned to each sensor electrode 3′, and each sensor electrode 3′ and the control portion 10 are connected by the wire and the FPC 4′. In the control portion 10, a change amount of the capacitance of the sensor electrode 3′ is converted into numerals, and when the numeral exceeds a predetermined threshold, it is determined that the finger is contacted. With this, in the control portion 10, it can be detected that the capacitance of which sensor electrode 3′ is changed, and therefore it can be detected that which touch switch portion is touched by the finger.
Further, as a touch switch, a capacitive touch switch provided with a glass substrate, a sensor portion formed at a side of an opposite surface opposite to a touch surface of the glass substrate, and a cover glass arranged at a side of the surface in which the sensor portion is arranged. The sensor portion includes a sensor electrode formed of metal thin film formed at a side of the opposite surface opposite to the touch surface of the glass substrate. The glass substrate and the cover glass are glass-sealed. The sensor portion is arranged in the glass-sealed space. An external connection terminal connected to the sensor portion and extended from the glass-sealed space toward an outside is arranged (see Patent Document 1).
As a touch switch having less number of components and good appearance, a touch switch provided with a sensor portion formed by a plurality of switch electrodes formed on a substrate and a switch electrode wire connected to the switch electrodes, a dummy electrode arranged around the sensor portion is known. The switch electrode is provided with a flat surface pattern and a design part in the flat surface pattern. Each of the sensor portion and the dummy electrode is formed of metal thin film (see Patent Document 2).
As a capacitive switch capable of suppressing that a gap between a transparent electrode and a non-transparent electrode is seen and capable of improving quality of design and decorativeness, a capacitive switch in which a plurality of the transparent electrodes is aligned by applying etching and laser processing to a silver nanowire painted on a film base material so as to form the gap between the transparent electrode and the non-transparent electrode, and a plurality of wire lines connected to the transparent electrode is formed by drying and curing silver ink at an edge portion on one surface of the film base material, and a protection layer is formed as an adhesive tape excluding acrylic acid, is known (see Patent Document 3).